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(5 BYA) Formation of the Solar System
Solar system was a swirling mass of gas and dust. Most of the material pulled together by gravity and formed the sun. Remaining gas, dust, and debris circled the sun and collided, eventually forming planets. -
(4.6 BYA) Continuing Formation of Earth
During a 400-million period, Earth grew larger as gravity pulled in more debris. -
(4 BYA) Earth Is Completed
Formation of Earth completed. Method of establishing the age of materials includes radiometric dating- measuring the quantity of a particular radioactive isotope in a material. -
(4 BYA) First Life on Earth
The first life appeared on Earth. -
(3.5 BYA) First Stromatolites
First stromatolites began to appear. Stromatolites are layered structures of colonies of cells such as Lynbgya. -
(3 BYA) Photosynthesis
Certain life forms became photosynthetic at this point. This allowed for the production of oxygen and later on, ozone, which blocked ultraviolet radiation and allowed a wide variety of life to emerge. -
(2.2 BYA) Earth as it is Today
At this point, Eath appeared much as it does today -
(2 BYA) CO2 Levels
At this point in history, the carbon dioxide levels on Earth reached the same level as they are today -
(2-1.5 BYA) Endosymbiosis
In these years, endosymbiosis, which is when an aerobic prokaryote is engulfed within an anaerobic prokaryote. The aerobic prokaryote provides aerobic energy, and the anaerobic prokaryote provides protection. This is what is believed to have been the start of what today is mitochondria and chloroplasts. -
(1 BYA) Ozone
Ozone (O3) is formed. This protected organisms from harmful UV rays so they could exist on land, and prevented harm to their DNA. -
(1665) Microscope
Robert Hooke used an early light microscope to view the cells of a cork oak tree. After using microscopes, many scientists came to the conclusion that microorganisms come from the “vital force” from the air -
(1688) Redi's Experiment
Francesco Redi conducted an experiment to disprove theory of spontaneous generation using flies and raw meat. -
(1768) Spallanzani's Experiment
Lazzaro Spallanzani performed an experiment boiling broth to test the theory of Spontaneous Generation. He boiled two flasks, and sealed the the top of one. The sealed one remained clear because the boiling killed all of the microorganisms. The open flask became cloudy because it was contaminated by microorganisms. However, the theory of Spontaneous Generation was kept alive for the next century. -
(1864) Pasteur's Experiment
Louis Pasteur performed an experiment that involved a flask with a curved but open neck. The neck prevented microorganisms from entering the flask. When broth was boiled in the flask, it remained clear until the neck was broken off. This contributed to the conclusion that spontaneous generation was not the correct theory, and that microorganisms came from other microorganisms. -
(1924) Oparin’s Hypothesis
Oparin’s hypothesis- Alexander I. Oparin and John B.S. Haldane proposed that the early atmosphere contained ammonia hydrogen gas, water vapor, and compounds made of hydrogen and carbon. -
(1952) Miller and Urey
Stanley L. Miller and Harold C. Urey set up an experiment using Oparin’s hypotheses as a starting point (used a chamber containing the gases Oparin assumed were present in the young Earth’s atmosphere). The experiment produced a variety of organic compounds, including amino acids. (1952) -
(1964) Fox
Sidney Fox performed extensive research on the physical structures that may have given rise to the first cells (including microspheres and coacervates) -
(1966) Margulis
Lynn Margulis proposed that early prokaryotic cells may have developed a mutually beneficial relationship, including endosymbiosis (small prokaryote was engulfed by and began to live and reproduce inside of a larger, anaerobic prokaryote). -
(1982) Cech
Thomas Cech found that a type of RNA found in some unicellular eukaryotes is able to act as a chemical catalyst, similar to the way an enzyme acts. RNA was the first hereditary molecule, and was able to cause its own replication.
